Test of proportional flow valve

Test of proportional flow valve

1、 Hydraulic test circuit

The typical test circuit of proportional flow valve is shown in Figure 10. The valve under test 4 in Figure 10 can be a proportional flow valve or a proportional throttle valve. If the valve under test is an electro-hydraulic proportional three-way flow valve, another pipe directly returning to the oil tank can be connected from the T port of the valve under test. At this time, pressure valve 2 acts as a system safety valve, while in other cases, valve 2 acts as a system overflow valve. The load unit composed of quick change-over valve 5, overflow valve 6 and throttle valve 7 is the load pressure regulating device of the system. Overflow valve 6 is the steady-state load pressure regulating device of the valve under test, and 8 is the dynamic flow sensor. The output control signal of electro-hydraulic proportional flow valve is flow, and its load interference signal is its front and rear pressure.

2、 Hydraulic test of electro-hydraulic proportional throttle valve

The test system refers to the hydraulic test circuit of the electro-hydraulic proportional flow valve shown in Figure 10. For electro-hydraulic proportional throttle valve (including proportional directional throttle valve), its controlled output parameter is the displacement or rotation angle of the main valve center. Therefore, when evaluating its steady-state and dynamic control characteristics and anti-interference ability, the displacement characteristics of the main valve core should also be investigated, rather than the usual volume flow characteristics. In addition, in this kind of valve, the flow is also affected by the change of load pressure and the fluctuation of oil source pressure, so the flow characteristic is only an auxiliary evaluation index. If it is necessary to investigate their flow characteristics, the pressure compensator can be used to keep the working pressure difference at the valve port of the tested valve at a certain value.

For proportional throttle valves and proportional directional valves, we should also pay attention to their limit power domain. When the pressure drop at the port of proportional throttle valve is large, the hydraulic force acting on the valve core will limit the flow through the port, especially in the case of single-stage valve, the performance test of limit power must be carried out. Figure 11 is the performance curve of the limit power of the four-way proportional directional valve. The test method is:

(1) Adjust the input electrical signal I to 95% of the maximum value, and then superimpose a low-frequency (generally 0.2 ~ 0.4hz), small sinusoidal signal (± 5% of the maximum value of the input signal).

(2) By slowly increasing the differential pressure of the valve, a continuous output flow pressure drop curve can be obtained. When the sinusoidal motion stops or the flow suddenly decreases, stop increasing the differential pressure of the valve, and mark this point on the diagram.

(3)在其他输入信号幅值下重复这个过程，如在额定流量的75%、50%和25%下，重复试验。

(4)连接那些标记点，就得到了一条极限功率曲线和一组输出流量阀压降的关系曲线（见图11）。

(5)如果是比例方向阀，在负向做同样的试验，也会得到一条类似的极限功率曲线和一组输出流量阀压降的关系曲线。